Category Archives: Piano Maintenance

Relative humidity may be a bit of a dry topic, but it is a key to understanding how pianos react to their environment and how you can best maintain your piano.

Let’s define Relative Humidity. According to the Piano Technicians Guild, “Relative humidity (RH) is the amount of moisture contained in the air, compared to the maximum amount of moisture that the air is capable of holding.” That “maximum amount” of moisture that the air can hold is determined by the temperature. The warmer the air, the more moisture it can hold. Therefore, if you increase the temperature without adding any extra moisture, the relative humidity decreases. This is because the “carrying capacity” of the air has increased while the actual amount of moisture has remained the same. If you think that’s just a theory that doesn’t hold water, please read on to find out exactly how humidity can throw your piano out of tune!

Many important parts of the piano are made of wood, and wood is particularly sensitive to changes in relative humidity. At higher humidity, wood absorbs moisture from the air, causing it to swell up. This has big effects on the piano’s soundboard, often made of Sitka spruce, and the bridges, which are made of layered (laminated) beech or maple. The piano’s strings stretch over the bridge, which transmits their vibrations to the soundboard. The vibration of the soundboard transduces the strings’ vibrations into air pressure changes. In other words, the soundboard passes energy from the strings to the air so we can hear it.

Two diagrams show a string stretching over the bridge, which is attached to the soundboard. The first shows a soundboard with less crown. The bridge does not press up into the string with as much force, which can lower the pitch of the string. This is what happens in dry environments at lower humidity levels. Image credit: Dampp-Chaser

Two diagrams show a string stretching over the bridge, which is attached to the soundboard. The second image shows a soundboard with an increased amount of crown. The bridge is pressing up into the string with more force, raising the pitch of the string. This is what happens at higher humidity levels. Image credit: Dampp-Chaser

The soundboard has a crowned or slightly arced shape, which pushes the bridge firmly against the strings. So, when humidity goes up, the soundboard swells up as the arc intensifies, and the amount of crown increases. This pushes the bridge more firmly against the strings, increasing the tension on the strings and making them go higher in pitch. In short, we expect the piano to drift sharp during the times of the year when it is more humid, and flat when it’s less humid. This effect is most pronounced in the middle of the piano’s range, where the soundboard’s crown is at its peak.

This image shows the piano’s steel strings crossing over the bridge. On the top of the bridge, the strings make their way through the bridge pins Image credit: Mario Igrec, Pianos Inside Out (In Tune Press, 2013)

At the other end of the strings, we tune the piano by turning the tuning pins, which control the tension of the strings. The strings are coiled around the tuning pins, which are driven into the pinblock, a multilayered wooden plank. Uncontrolled fluctuating humidity can also cause damage to the pinblock, which will have a negative effect on the piano’s tuning stability. This damage can include loosening of the tuning pin holes. The pinblock can crack and its layers can come apart (delaminate).

This image shows a tuning pin held in the pinblock in its proper position, slightly angled away from the string. Image credit: Dampp-Chaser

A damaged pinblock can allow the string to pull the tuning pin out of its proper position, and weaken the tight fit between the pin and the pinblock Image credit: Dampp-Chaser

Here’s what you can do to help fight the effects of fluctuating humidity and improve your piano’s tuning stability. First, get your piano tuned! It is recommended that pianos be tuned at least twice a year. Pianos need to be “trained” to stay in tune, especially when they are new– so having your piano tuned regularly will help keep it stable. Second, position your piano away from heaters, air conditioners, windows, or any other location where it will be subject to environmental extremes.

Lastly, consider a humidity control system. The Piano Life Saver system from Dampp-Chaser can be installed in grands or uprights. It consists of a Humidistat, a Humidifier, and a Dehumidifier. The Humidistat constantly monitors the humidity level and activates the Humidifier or the Dehumidifier as necessary, in order to keep the relative humidity level inside the piano near the recommended 45%. This will make your piano’s tuning, regulation, and touch as stable as possible, allowing you to focus on making beautiful music.

Right now you can set up an appointment to install a humidity control system in your piano with one of our fine technicians. Book online today.

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This is part one of what I hope to be a ten-part series guiding us through the book Pianos Inside Out by Mario Igrec.

Many piano technicians will consult with this book on a regular basis as needed, but sometimes its worthwhile to work through a text searching for gaps in our knowledge, undiscovered pearls of wisdom, and just to gain a more solid foundation in the craft of piano work.

This endeavor is meant to aid other piano techs and spark interaction and camaraderie. Any feedback you, as a reader, have regarding the presentation or format is much appreciated.

Okay! Moving on…

It’s time to start reading! The first section we’ll address is pages 1-50. That’s Chapter 1 on History and half of Chapter 2 about Design and Construction. The goal is to read through this in one week. This section covers the beginnings of what is considered the modern piano and some variations along the way. Then we move on to the composition of the piano, including its supportive structure, strings, bridges, and soundboard. The remaining structure is covered in the next section.

Here is a brief outline of the content of these pages, followed by some study questions. You can use this to prime your brain before your reading or for reviewing after you read. Keep in mind that many of the study questions can only be answered by reading the text of the actual book. So dive in.

The answers are in the book, and it’s more motivating to find them yourself if you don’t have them readily available so they are not posted here. However, you can sign up to keep abreast of this project and I’ll forward a document with the answers so we can compare notes.

Chapter 1: History

The piano was born in 1700 when Bartolomeo Cristofori, of Florence Italy, installed the first piano action into a harpsichord. The purpose was to alter the instrument so that strings could be struck by hammers instead of plucked by plectra. This allowed for variability in volume depending upon how hard keys were pressed.

Around the same time a similar instrument was becoming popular called the pantaloon. It was a dulcimer modifies such that, again, strings could be struck by hammers, this time instead of by the traditional dulicimer mallets. The instrument was named after a famous dulcimer player called Hebenstreit Pantalon.

Throughout the remainder of the 18th century, pianos grew in popularity, spread to various european locales, and were modified in several ways. The 1700’s saw the introduction of pedals, for example. Vertical pianos evolved from the clavicytherum, a type of upright harpsichord. In the latter half of the 18th century, the industrial revolution began to influence piano design and construction.

As the century turned even more advances in technology and a rising middle class meant that more pianos could be constructed and sold. Pianos began to be built in the United States. Bach, Haydn, Mozart and Beethoven all had the chance to interact with the developing instrument and as the 1800s progressed an increasing number of compositions were intended for the piano.

Through the first half of the 19th century the piano gradually became bigger and louder instrument. The range of the keyboard increased from 5 octaves to 6.5. The cast metal plate was introduced. The double escapement action was invented by Sebastien erard. The overall tension held within the instrument increased. Inventions and patents to improve the piano proceeded at a rapid pace. Agraffes, cross-stringing, the capo tasto bar, felt hammers, and technologies to aid in manufacturing things like hammers were all patented, introduced in this time.

In the second half of the 19th century Steinway began in America and then after success there began manufacturing in Europe as well. Also at this time the square piano became popular but quickly lost favor because of many design flaws. As the 20th century approached, pianos became quite a popular instrument, and very profitable to manufacture and sell. Popularity continued to grow in the early 20th century. However, as the phonograph, radio, motion picture, and television industries invaded, and because of the great depression and WWII, the piano lost some favor. Since WWII piano popularity has had swells within various markets independently, such as in Eastern Europe, Japan, Korea and China.

Chapter 2: Construction and Design

According to Mario Igrec “piano design history has been a struggle to more efficiency convert a finger’s force into acoustic energy.” This can be achieved through a number of manners: increased string tension, soundboard tension/compression, and mass of hammers.

The rim of the piano consists of an outer and inner part. The outer rim is essentially a part of the case of the grand piano. There are two manners of constructing the rim. Composite rims are constructed from small segments and continuous laminated rims consist of a series of laminated boards that are all at once bent around a mold to form the shape of the pianos case. The rim of a grand piano supports its structure just as vertical beams in an upright do the same. A dense and rigid rim or frame maximizes volume and sustain.

Beams of spruce join a rim/frame with the belly rail. The belly rail provides a rail of support to which the soundboard can be glued.

The pin block consists of laminated sheets of wood with grans sequentially angled at 45-90 degree differences to one another. The pinblock must grip tuning pins firmly and transmit the tension of the strings to the plate and rim. A pin block is generally 1.25” to 1.5” thick [31 to 38mm]. In a grand piano a pinblock can be installed in 3 ways. In order of increasing quality you can have a floating, regular fit or full fit pinblock. Each style adds an extra point of structural attachment to the plate, rim, and stretcher respectively.

The strings, bridges, soundboard and plate generate sound. Each of around 230 strings – holds around 160-200 lbs of tension. Strings are typically made of high-carbon steel and sometimes nickel plated. Bass strings have a copper winding, to allow for increased mass (slower oscillation) without unmanageably thick strings.

The bridge lies compressed between the strings and the soundboard and transmits vibrations between the two. A stiff soundboard reflects some energy back the strings, which allows them to sustain longer. The bridge has often has a separate root and cap portion. A separate cap can be shaped and notched easily and replaced if it cracks. Bass strings are longer and extend toward the edge of the soundboard where it is more rigid. In order to increase flexibly in the area where the bass resigntes a shelf sometimes used to allow the longer strings to contact a more central (flexible) part of the soundboard.

Bridge pins are made of steel, often with brass plating to reduce friction. Notches in the bridge allow strings to vibrate freely where they contact the bridge pins. If notching does not create the same termination point at the bridge pin and the bridge notch this can lead to false beats. Sometimes termination points on the bridge are engineered to create unequal speaking lengths. Unequal lengths cause slight interferences among the sound waves from each string. This means the strings resonate with one another less effectively, transfer energy to the soundboard less effectively, and therefore can have a longer sustain.

The soundboard is sometimes mischaracterized as an amplifier, when in fact it is only a transducer of vibrations from the strings into the air. A good soundboard will effectively impede the vibrations of the strings, allowing for a short attack sound and a long sustain. A well designed soundboard’s resonances will be carefully tweaked so that the tone quality from the various strings in the piano is consistent. Spruce soundboard material is rigid along its gran but less so across the grain, therefore soundboard ribs are installed across the grain to create an isotropic diaphragm, in which rigidity is relatively equal in all directions.

The next post continues to work through chapter 2 on design and construction.

Study Questions:

(Many can only be answered by reading the text of the actual book. So dive in.)

pages 1-10:

1. What year marks the invention of the piano?
2. Who is credited with inventing it?
3. In which century were JS Bach, Haydn, and Mozart prominent? Which of them had the opportunity to use the invention of the piano?
4. There was an instrument called the Pantalon. Where does the name come from?
5. In what country was the piano invented?

pages 11-20:

6. Around what time did pianos start to be made in America?
7. What major development in piano construction allowed for louder pianos?
8. Around what year was it developed?
9. Who invented the agraffe in 1808? What other major invention is he responsible for?
10. Piano design history has been a struggle to do what?

pages 20-30:

11. According to Mario Igrec, what are the two most valued characteristics in pianos today?
12. The quality of these two characteristics is proportional to what?
13. True or False. The outer rim can be added after pin block, soundboard, bridges and strings.
14. What type of wood might you find in the dense rim of an expensive pianos?
15. What re the two main types of rims? How are they constructed

pages 30-40:

16. How thick is the typical pin block?
17. When bridges transmit vibrations from the strings to the soundboard, but also reflect much of that energy back to the strings, what tonal outcome does this create?
18. What is described by the following statements? Easier to shape and notch than a vertically laminated root. Can be replaced if it cracks. Can be used to modulate the stiffness of the bridge.
19. Which piano maker patented the continuous curved bridge?
20. What is described by the following statement? There are three types: regular floating, fit, full fit. Which is best?

pages 40-50:

21. What is the purpose of a bass bridge shelf or apron?
22. What is the purpose of having unequal speaking lengths in unisons?
23. How will a lower cutoff frequency in its soundboard improve a piano’s sound?
24. Which is a more appropriate term for the soundboard? Transducer or amplifier? Why?
25. What is a typical number of degrees for downbearing?

If you don’t have the book, GET IT! But if you’d like to preview further then here are PDF excerpts from various chapters of this book, as posted on the book’s web page:

After my short but full stay in Cartagena, I flew into New York City. I was excited to return to the Floating Piano Factory home base, catch up with friends, and re-discover the beauty of this town. While I was there, I stayed with friends in Long Island, a couple that I came to know through a long chain of music-related moments…

Okay, so there were actually a few more things that happened before I left Arequipa.

I returned to La UNSA to work with the music students once again. This time, we pulled apart a piano so they could see how it’s assembled. How the various pieces all fit together.

This is a rare opportunity. As a student, you don’t usually get the chance to take a piano completely apart, because once you open it up and start poking around, it can get really delicate. There’s a lot you have to learn in order to explore without doing any damage.

One of the first important steps in grand piano action regulation is the adjustment of glide bolts. The glide bolts sit at four points distributed lengthwise along the center rail of the grand piano action. They have a tuning-pin-shaped protrusion towards their top, a central threaded portion that allows for up-down adjustment, and smooth rounded bottom. The bottom of the glide bolt both provides support for the center rail of the action and allows the piano to easily glide from left to right when the una cord pedal is depressed. Continue reading →

I’ve recently returned from some extensive travels over several weeks. This is why it’s been quiet on the blog for a while, but now we’re back online, and there are many new stories to share. New adventures, new friends, and of course, new pianos.

The next several posts will cover the entire journey, city by city. After departing from Arequipa in early June, I stopped in Lima, Bogotá, Medellín, Cartagena, New York, Philadelphia and Hong Kong—then returned by retracing my path.

In this set of video tutorials Macho and Neway from Floating Piano Factory in Hong Kong show us how to replace hammer return spring cords on a Yamaha U1 upright piano. It is quite common for these cords to wear out and break. In this piano, virtually all of them have become useless! Continue reading →